Lung area--volume models in relation to the recruitment--derecruitment of individual lung units.

The objective of this study was to reconsider some of the previous experimental results in terms of simple geometric models in order to determine if any of the apparent conflicts could be explained within a more unified concept. These models allow individual lung units and the entire lung to expand differently with regard to their area-volume relationship. The effect of a recruitment-derecruitment process as the lung inflates-deflates is also considered. Examples are used to illustrate how some of the apparent conflicts found in the literature may arise from whether or not recruitment and derecruitment take place during lung expansion and contraction.